A conventional surface protective layer and interlayer insulating layer for a semiconductor device includes a polyimide resin having excellent heat resistance, electrical properties, mechanical properties, and the like. The polyimide resin has recently been used as a photosensitive polyimide precursor composition to be coated easily. The photosensitive polyimide precursor composition is coated on a semiconductor device, patterned by ultraviolet (UV) rays, developed, and thermally imidized, easily providing a surface protective layer, an interlayer insulating layer, and the like. Accordingly, the polyimide resin may remarkably shorten a processing time, compared with a conventional non-photosensitive polyimide precursor composition.
A photosensitive polyimide precursor composition can be applied as a positive type in which an exposed part is dissolved by development and as a negative type in which the exposed part is cured and maintained. The positive type may be developed by a non-toxic alkali aqueous solution and thus, preferably uses. The positive photosensitive polyimide precursor composition includes a polyimide precursor of polyamic acid, a photosensitive material of diazonaphto-quinone, and the like. However, the positive photosensitive polyimide precursor composition has a problem that a desired pattern is not obtained because of too high solubility of carbonic acid of the polyamic acid in an alkali. In order to solve this problem, a material including phenolic hydroxyl acid introduced instead of carbonic acid by esterifying polyamic acid with an alcohol compound having at least one hydroxyl group has been suggested (Japanese Patent Laid-Open Publication No. 10-307393) but has a problem of insufficient developability and thus, layer loss or resin delamination from a substrate.
Recently, a material prepared by mixing a polybenzoxazole precursor with a diazonaphtoquinone compound (Japanese Patent Laid-Open Publication No. 1994-060140) has drawn attention but has a problem of hardly obtaining a desirable pattern due to big layer loss of an unexposed part after the development, when the polybenzoxazole precursor composition is actually used. However, when the molecular weight of the polybenzoxazole precursor is increased to improve this problem, the layer loss of the unexposed part is reduced, but a development residue (scum) in an exposed part is generated and thus, may deteriorate resolution and lengthen the development on the exposed part. In order to solve this problem, it has been reported that the layer loss may be suppressed by adding a certain phenol compound to a polybenzoxazole precursor composition (Japanese Patent Laid-Open Publication No. 9-302221 and Japanese Patent Laid-Open Publication No. 2000-292913). However, since the suppression effect of the layer loss of the unexposed part is insufficient, research on increasing the suppression effect of the layer loss along with preventing generation of the development residue (scum) is required. In addition, since the phenol for controlling solubility causes a problem of being decomposed or occurring a side reaction at a high temperature during the thermosetting and thus, does a huge damage on mechanical properties of a resultant cured layer, research on substituting the phenol as a dissolution controlling agent is still required.
The positive photosensitive resin composition including the polybenzoxazole precursor may be applied to an organic insulator or a barrier rib material in a display device field. A liquid crystal display device, one kind of a display device, has lots of advantages of being light and thin, costing low, being operated with small consumption of electricity, having excellent junction with an integrated circuit, and the like and thus, has been widely used for a laptop computer, a monitor, and a TV image. This liquid crystal display device includes a lower substrate having a black matrix, a color filter, and an ITO pixel electrode and an upper substrate having an active circuit portion consisting of a liquid crystal layer, a thin film transistor, and a capacitor layer and an ITO pixel electrode. The color filter is fabricated by sequentially laminating a black matrix layer with a predetermined pattern on a transparent substrate to block a light among pixel boundaries and a pixel part consisting of a plurality of colors (in general, three primary colors of red (R), green (G), and blue (B).
In addition, an organic light emitting diode (OLED) actively developed in recent times is arranged as a pixel with a matrix format. These pixels are arranged to emit the same color to fabricate a single color display or as three primary colors of red (R), green (G), and blue (B) to display various colors.
On the other hand, many attempts have been recently made to develop a display device having high contrast ratio and high luminance. One of the attempts is to form a black filter layer between color patterns but has a problem of hardly realizing a high aperture ratio and bringing about low heat resistance and insulating properties. Then, another attempt of securing a high aperture ratio by making a non-light emitting region black and simultaneously, improving a contrast ratio and visibility but has a problem of deteriorating inherent properties of an insulation layer because a colorant is dissolved in a large amount. In addition, an inorganic pigment as carbon black and the like used for a black mill-base, a colorant, in general has excellent light shielding properties but has a problem of deteriorating insulating resistance properties, which is not appropriately applied to an insulation layer for an organic light emitting diode. On the other hand, an organic pigment relatively consists of a pigment mixture realizing a black color and thus, has better insulating resistance properties than the inorganic pigment but needs to be more included than the inorganic pigment in a photosensitive resin composition to accomplish equivalent light shielding properties and more possibly, deteriorates pattern developability and produces a residue.
Accordingly, development of a new photosensitive resin composition having no aforementioned problems is required.